Field of the Invention
The present invention relates to a power transmission apparatus for a vehicle. More particularly, the present invention relates to a power transmission apparatus for a vehicle which can improve power delivery efficiency through a fixed gear ratio mode and control to an optimal driving point through a variable gear ratio mode by applying a motor/generator and a planetary gear set for an electronic continuous variable transmission (E-CVT) to a double clutch transmission (DCT).
Description of Related Art
In a vehicle, environment-friendly technology is a key on which the survival of the future automobile industry may greatly depend, so vehicle manufacturers are devoting their efforts to the development of environment-friendly vehicles so as to meet required environmental and fuel efficiency regulations.
As such a future type of vehicle technology, there are, for example, an electric vehicle (EV) which uses electrical energy, a hybrid electric vehicle (HEV), and a double clutch transmission (DCT) which is configured to enhance efficiency and convenience.
In addition, vehicle manufacturers are trying to commercialize a predetermined technology such as an idle stop and go (ISG) device and a regenerative braking device, as a means for enhancing the efficiency of a driving force transfer system in an effort to enhance the performance of fuel efficiency while meeting exhaust gas regulations of each country.
The ISG device uses a technology for stopping the engine while the vehicle stops and for starting the engine when the vehicle starts. The regenerative braking device uses a technology for driving a generator which uses the kinetic energy of the vehicle instead of braking based on a conventional way of friction when braking and decelerating the vehicle, and for storing the generated electrical energy in a battery and then reusing such stored electrical energy.
In addition, the hybrid electric vehicle to which the transmission of the present invention may be applied is a vehicle which uses two or more power sources, and may be combined in various ways. The hybrid electric vehicle may be formed as a hybrid type of a gasoline engine or a diesel engine which uses existing fossil fuel and a motor/generator which is driven by electrical energy.
In addition, as a transmission which may be applied to such a hybrid electric vehicle, there is, for example, a double clutch transmission (DCT). The DCT is capable of increasing efficiency and improving convenience by applying two clutches to the manual transmission structure.
Specifically, the DCT is a transmission wherein gear shifting is performed in such a way that odd-numbered gears and even-numbered gears are alternately operated using two clutches. The mechanism wherein the gear shifting of the odd-numbered gears and the even-numbered gears is alternately performed may improve a torque disconnection effect during the gear shifting of the existing manual transmission (MT) and the automated manual transmission (AMT).
However, the DCT may have a lot of clutch damage and energy loss due to slipping of the clutch at the time of startup. When the vehicle starts on an incline, the vehicle may have a large backward force due to the slipping of the clutch, and thus problems may occur in terms of safety. Since it needs to make shifting quickly due to the heat capacity of the clutch, the impact during the gear shifting increases as compared with the automated transmission.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.